1. Field of the Invention
This invention relates to a split-type internal combustion engine and, more particularly, to an exhaust passage structure for such an engine.
2. Description of the Prior Art
Split-type internal combustion engines are already well known which include a plurality of cylinders split into first and second groups, means responsive to engine low load conditions for cutting off flow of fuel and fresh air to the second group of cylinders so as to hold them suspended, and an exhaust passage provided at its downstream end with a catalyzer. For reduction of pumping loss in the suspended cylinders, exhaust gases are re-introduced into the suspended cylinders while the engine is under low load conditions. Although such split-type engines are advantageous in high fuel economy, as the amount of exhaust gases recirculated increases, the temperature of the exhaust gases passing through the catalyzer becomes too low to provide optimum performance of the catalyzer, which results in poor exhaust emission characteristics. This difficulty stems mainly from the current designs of the exhaust passage.